Hydrogenation of aryl carboxylic acids



' basic acids.

Patent ed Aug. 8, 1944 2,355,219 HYDROGENATI'ON or AnYncARBoxyLm ACIDSVladimir N. Ipatiefl and Vladimir Haensel, Riverside, Ill., asslgnors toUniversal Oil Products Company, Chicago, Ill.

ware

, a corporation oi Dela-,

I No Drawing. Application May 31, 1943, Serial No. 489,153

Claims. (01. 260-668) This invention relates to the use of particularcatalytic materials in reactions involving hydrogenation of arylcarboxylic acids.

An object of this invention is the hydrogenation of aromatic carboxylicacids so as to produce therefrom aromatic hydrocarbons or alkylatedaromatic hydrocarbons having the same number of carbon atoms permolecule as present in said aromatic carboxylic acids.

Another object of .this invention is the hydrogenation of an aromaticcarboxylic acid in the presence of a catalyst produced by subjecting toreduction a composite formed from copper oxide and at least anotheroxide selected fromthe group consisting of aluminum oxide and zinc oxidewhereby to convert the carboxylic acid group into a methyl group withsubstantially no other influence on the aromatic carboxylic acid.

A further object of this invention is the pro--' duction of an aromatichydrocarbon by the hydrogenation of an aromatic monocarboxylic acid1,2,4-trimethyl-5-benzoio.

in the presenceof a catalyst comprising essentially a composite orreduced copper and at least one 01. the oxides selected from the groupconsisting of aluminum oxide and zinc oxide.

A still further object of this invention is the hydrogenation ofa memberselected from the group consisting oi. aryl carboxylicacids andanhydrides of aryl carboxylic acids to produce alkyl aryl compoundsincluding alkyl aromatic hydrocarbons, alkyl aryl carbinols, aromaticesters, and aromatic carbonyl compounds such as aromatic aldehydes.

In one specific embodiment the present inven-- tion comprises a processfor producing alkylated aromatic hydrocarbons by reacting an aryl car-'boxylic acid and hydrogen in the presence of a catalyst comprisingessentially a composite of reduced copper and at least one of theoxides" Aryl carboxylic acids which are utilizable as starting materialsin the present process maybe obtained from any source and may comprisemonocyclic and polycyclic aromatic carboxylic acids including both themonobasic and also poly- Aromatic carboxylic acids which may behydrogenated'as herein set forth also include compounds in which one ormore of the hydrogen atoms of an aromatic ring may be consldered to bereplaced by an organic acid group generally referred to. as a carboxylgroup. Aromatic carboxylic acids also include the aryl fatty acids suchas phenyl acetic acid, the different isomeric phenyl propionic acids,etc. in which one of the hydrogen atoms of the alkyl vgroup 01' anNaphthalic Some aryl carboxylic acids Melting int Aromatic acids p0Boiling point Mono-carbozulic "'C'. Benzoic o-Toluic..-

P o-Ethylbenzoic.-. m-Ethylbenzoic .mmyir 1,2-dimethy -3- 1,3-dimethy-2-benzoic 1,4-dimethy -2- benzoic o-n-Ptopyl bcnzoi cp-n-Propyl benzo1co-iso-Propyl benzoic.

1,3,5-mesitylene carboxylic 1,2,3.4-tetramethyl-5-benzo1c.Pentamethylbenzoic Phenyl-fatiy acids Acid: of polycyclic aromatic:

a-Naphthoic a-Naphthoic B-Naphthyl Acetic B-Anthracene carboxylioa-Anthracene carboxylio Aromatic dicarbozwliq acids Phthalic.

lsophthalicn Terephthalic The process of the present invention is alsoaryl carboxylic acids. The products obtainable by such :hydrogenationtreatment of these acid anhydrides are essentially the same as thoseproduced by hydrogenation of the corresponding aryl carboxylic acid.

Composites of the above-indicated materials utilizable as.catalysts inthe hydrogenation of aryl carboxylic acids and their anhydrides may bemade by precipitating the carbonates of zinc .nium carbonate, atordinary or elevated temperatures. Aluminum hydroxide may be preciptated similarly either in the presence or absence of the carbonates ofcopperand zinc. The pre-' cipitated material so obtained is filtered,care-'- For purposes of reference some of the aromatic fully washed withwater to remove water soluble and to reduce a substantial proportion ofthe resulting copper oxide to metallic copper in a form havingrelatively high hydrogenating activity. The metal carbonate may also bedecomposed by heating in air prior to being heated in hydrogen to efiectreduction.

The composite catalytic material may also be prepared by coprecipitatingcopper carbonate, zinc carbonate, and/or aluminum hydroxide; or for thepreparation of a copper oxide-zinc oxidealuminum oxide mixture, the zinccarbonate may be first precipitated on alumina followed by precipitationof the basic copper carbonate on the mixture. The proportions of thevarious components may be varied considerably. A good catalyst isprepared containing 25 parts by weight of zinc, 25 parts by weight ofcopper, and 50 parts by weight of alumina; while others: consist ofapproximately equal parts by weight of zinc, copper, and alumina.Similarly, composites of copper and alumina also yield highly activecatalysts which after reduction with a hydrogencontaining gas compriseessentially copper and alumina, said composites containing from about 1to about 50% by weight of alumina mixed with reduced copper.

The catalyst granules or pellets of the type hereinabove described maybe used as filling materials in suitable heated reactors through whichthe aryl carboxylic acid and hydrogen are passed at a temperature offrom about 200 to about 350 C. and under a pressure of from about 25 toabout 300 atmospheres. Under some circumstances it-may be advantageousto commingle the aryl carboxylic acid with a solvent such as ethylalcohol, dioxane, etc. before it is subjected to hydrogenation in thepresence of the catalyst. However, when analcohol is present in thereaction mixture, some of the carboxylicacid may" react therewith toform an ester. As the conditions of operation are not necessarily thesame for the hydrogenation of the different aryl carboxylic acids, thecatalyst temperature. charging rate of said carboxylic acid, and ratioof hydrogen to carboxylic acid employed are chosen to give a high degreeof conversion to alkylated aromatic hydrocarbons with a relatively smallor it may be mixed with the hydrogen in a so-- called fluidized type ofoperation; and thereafter the hydrogen-catalyst mixture may be contactedwith pre-hea'ted aryl carboxylic acid. After such a hydr igenationtreatment in the presence of a powdered catalyst the reaction productsare separated from the catalyst and fractionated to recover the desiredproducts and to separate unconverted aryl carboxylic acid and usedcatalyst which are recycled to the reaction zone for further use. 'Apowdered catalyst may thus be used in either batch or continuoushydrogenation of an aryl carboxylic acid.

The process of this invention is particularly advantageous for producingaromatic hydrocarbons from aryl carboxylic acids since the compositecatalyst containing copper and at least one of the oxides selected fromthe group consisting of aluminum oxide and zinc oxide is able tocatalyze the hydrogenation of the carboxylic acid group to a methylgroup without simultaneous hydrogenation of the aromatic ring oraromatic rings to naphthenic or cyclohexane rings. A number of catalystsof the prior art have been utilized in hydrogenations of aryl carboxylicacids, but with these catalysts the aromatic rin underwent reduction toa cycloparafiin ring which is generally referred to as a naphthene ring.The catalysts of the present process, however, are sufficiently activeto catalyze the conversion of the carboxyl group or carboxyl groups, incase a polycarboxylic acid is being hydrogenated, substantially withoutafiecting the aromatic nucleus of the aryl carboxylic acid.

' erally hard and resistant to breakage, have relaof aromatic acids.

as after a long period of service, it is usually ad- .lowed to cool andsettle.

tively high activities, and do not undergo excessive carbonizationduring use in hydrogenation When carbonization occurs,

visable to burn the carbonaceous deposit from the catalyst by treatmentwith a gas of controlled oxygen concentration followed by heating in areducing gas such as hydrogen, carbon 'monoxide, a mixture of hydrogenand carbon monoxide; Or a gas mixture containing a substantial amount ofa reducing gas.

The following examples are given to indicate results obtained by theprocess although these data are not introduced with the intention ofunduly limiting the generally broad scope of the in 12 liters of water.Another solution was prepared by dissolving 770 grams of ammoniumcarbonate monohydratein 5 liters of water. Then the ammonium carbonatesolution was added slowlywith stirring to the solution containing coppernitrate and aluminum nitrate. Upon completion of the precipitation theentire reaction mixture containing precipitated copper carbonate andaluminum hydroxide was heated at 70 to C. during a period of between 0.5and 1 hour. Upon reaching 80 C. the heating was discontinued and theprecipitate was al- Then approximately 12 liters of solution weredecanted from the precipitate which was then washed by the addition of12 liters of distilled water. This procedure of washing by decantationwas repeated four times and finally the precipitate was separated fromthe wash water by filtration with suction. The filter cake so obtainedwas washed again with 2 liters of water and separated by filtration. Thewashed catalyst was then dried at 240 C. during 13 hours in aself-regulating drying oven. The dried material so obtained had a darkbrown color and weighed approximately 500 grams.

water.

The dried material was then reduced and of the material was placed in aglass tube heated in a horizontal furnace. A mixture of 2 volumes ofnitrogen and 1 volume ofhydrogen was passed over the catalyst at atemperature of 1'70 to 180 C. during 48 hours after which the reductionwas complete as evidenced by the fact that water was no longer presentin the eflluent gases. The mixture of nitrogen and hydrogen was thendisplaced by nitrogen and thereafter a mixture of 60% nitrogen and 40%air was passed over; the reduced material at room temperature forapproximately 12 hours. The resultant material which was black in colorwas a stabilized active catalyst.

4 70 grams of benzoic acid, 63 grams of ethyl alcohol, and 15 gramsofthe above-described reduced and stabilized copper-alumina catalystwere placed in a rotatable steel autoclave, hydrogen was added to 100atmospheres initial pressure, and the resultant reaction mixture was Thepredominant reaction was the formationof stabilized as follows.Approximately 300 grams heated and rotated at 300 C. for a period of 4hours. After this treatment, the autoclave and contents were cooled toroom temperature and the reaction product was removed and analyzed. Thereaction product consisted of toluene and ethyl benzoate in therespective yields of 39% and 30% of the theoretical based uponthereduced and stabilized copper-alumina catalyst described in Example Iwere placed in a steel autoclave to which hydrogen was added to 100atmospheres initial pressure, and the reaction mixture was then heatedto 300 C. for four hours. The reaction product contained toluene in ayield of 41% of the theoretical together .with small amounts of benzylbenzoate, benzaldehyde, and benzyl alcohol. Since the benzyl benzoate,benzaldehyde, and benzyl alcohol are apparently intermediates in theformation of toluene from benzoic acid, it is believed that the yield oftoluene would'have been increased appreciably by increasing the time oftreatment with hydrogen at the reaction temperature.

The results'of this'example show that the hy drogenation is selectiveand does not involve 'the ployed.

4 Example III 80 grams of phthalic .anhydride and 15 grams of thereduced and stabilized copper-alumina catalyst described in Example Iwere placed in a steel autoclave of 850 cc. capacity under an initialhydrogen pressure of 150 atmospheres and heated to 300 C. for fivehours. The 79.6 grams of recovered liquid product contained 8 ams of Theliquid product was dried and was then separated by fractionaldistillation into the following fractions having the propertiesindicated. I

' Refractive Per cent by Fraction No. Boiling point, G. volume indexTotal 100.0

orthoxylene although some toluene was also formed. The foregoingspecification and examples indicate the character and value of thepresent process, althoug'h it is not intended that either section shouldunduly limit the generally broad scope of the invention.

We claim as our invention: a

1. A process for producing alkyl aryl compounds which comprises reactinghydrogen and a member selected from the group consisting of arylcarboxylic acids and anhydrides' of aryl carboxylicacidsunderhydrogenating conditions in the presence of a catalystproduced by subjecting to reduction a composite comprising copper oxideand at least another oxide selected from the group consisting ofaluminum 'oxide and zinc oxide.

2. A process for producing alkyl aryl compounds which comprises reactinghydrogen and an aryl carboxylic acid under'hydrogenating conditions inthe presence of a catalyst produced by subjecting to reduction acomposite comprising copper. oxide and at least another oxide selectedfrom the group consisting of aluminum oxide and zinc oxide.

3. A process for producing alkyl aryl compounds which comprises reactinghydrogen and an anhydride of an aryl carboxylic acid under hydrogenatingconditions in the presence of a catalyst produced by subjecting toreduction a composite comprising essentially copper oxide and at leastanother oxide selected from the group consisting of aluminum oxid andzinc oxide.

4. A process for producing an alkyl aromatic hydrocarbon which compriseshydrogenating an aryl carboxylic acid in the presence of a' catalystproduced lay-subjecting to reduction a composite comprising essentiallycopper oxide and at least another oxide selected from the groupconsisting V of aluminum oxide and zinc oxide.

hydrocarbon which comprises reacting an aryl carboxylic acid andhydrogen at a temperature of from about 200 to about 350 C. in thepresenc of acatalyst produced by subjecting to reduction a compositecomprising essentially copper oxide and at least another oxide selectedfrom the group consisting of aluminum oxide and zinc oxide.

6. A process for producing an alkyl aromatic hydrocarbon which comprisesreacting an aryl carboxylic acid and hydrogen at a temperature of fromabout 200 to about 350C. under a pressure .of from about 25 to about 300atmospheres in the presence of a catalyst produced by subjecting toreduction a composite comprising essentially copper oxide and at'leastanother oxide selected from the group consisting of aluminum oxide andzinc oxide.

7. A process for producing an alkyl aromatic hydrocarbon which comprisesreacting an aryl carboxylic acid and hydrogen at a temperature of fromabout 200 to about 350 C. under a pressure ofirom about 25 to about 300atmospheres in the presence of a catalyst produced by subjecting toreduction a composite comprising essentially a major proportion byweight of copper oxide and a relatively minorv proportion of at of fromabout 200 to about 350 C. under a pres sure of from about 25 to about300 atmospheres in the presence or a catalyst produced by subjecting -toreduction a composite comprising essentially copper oxide and aluminumoxide.

sentially copper oxide, zinc oxide, and aluminum oxide.

10. A process for producing an alkyl aromatic hydrocarbon whichcomprises reacting an aryl carboxylic acid and hydrogen at a temperatureof from about 200 to about 350 C. under a pressure of from about 25 toabout 300 atmospheres in the presence of a catalyst produced bysubjecting to reduction a composite comprising esio esentially copperoxide and zinc oinde.

VLADIMIR N. IPATIEFF. VLADIMIR HAENSEL.

